CVE-2026-21865
Discourse topic conversion permission vulnerability for moderators
Description
Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, moderators can convert some personal messages to public topics when they shouldn't have access. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. As a workaround, site admin can temporarily revoke the moderation role from untrusted moderators or remove the moderator group from the "personal message enabled groups" site setting until the Discourse instance has been upgraded to a version that has been patched.
How to fix CVE-2026-21865
To remediate CVE-2026-21865, upgrade the affected package to a fixed version below.
- —upgrade to 3.5.4 or later
Is CVE-2026-21865 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 3.5.4, >= 2025.11.0, < 2025.11.2, >= 2025.12.0, < 2025.12.1, >= 2026.1.0, < 2026.1.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N |